Tracking & Killing Bot Networks

In a previous blog I discussed how one of the more enjoyable parts of my day-to-day malware rituals also involves the tracking and killing of command and control bot networks. Recently I have begun automating this process a bit; I have created a series of scripts that extract irc servers, port numbers and channels from malware as it comes in and then checks if the irc server is still online, a custom bot then logs into the server, queries the active channels and determines how many zombies are active on the network. If an irc server is determined to be active with zombies actively connected, the server is then reported to the abuse address listed in the whois information for the servers IP Address.

The automation of this process is something I have had on my todo list for a little while but finally stopped procrastinating it and got it done. The real advantage of it being automated now is I can easily generate a tangible set of information that allows for me to see how many bot networks are present in the malware I process daily, weekly and monthly, how many of those networks are still active and more importantly how many of those networks have active zombies still connected. Likewise, as I’ve discussed previously, I am working on a threat portal and having the irc c&c data processing automated will more easily allow me to put that information on the threat portal and integrate it into the aggregate threat feed that the portal will offer for route/firewall/DNSBL drops.

Here are some statistics on IRC command and control networks as seen in the malware processed by me in the last 30 days:Total Processed Malware (30d): 607Total IRC C&C Servers: 251Total Online IRC C&C Servers (as of 08/17/10): 118Total Online IRC C&C Servers with Active Zombie Hosts: 30Total Zombies Observed on Online IRC C&C Servers: 1,679 (55 average per server)

There are some notable observations, out of the total of 251 noted IRC C&C servers, only 118 of them are still online, of those 118 that are still active, 64 of them utilize free DNS naming services and/or dynamic dns services, the other 54 create C&C channels on established public IRC networks or use the DNS name of compromised hosts running an IRC server. Most every one of the 133 now inactive IRC servers used IP addresses within the host malware script, a small majority used DNS names of compromised hosts.

It goes without saying that by using public DNS services / dynamic DNS services, it allows attackers the flexibility to quickly recover a C&C server and its participating zombies in the event of the host server being shutdown. Further, a number of more mature IRC C&C bots will continue reconnection attempts periodically when disconnected from the host C&C server, further increasing the chance of fully recovering the zombie network for the attacker.

Also increasingly, PHP is becoming more common as a language of choice for C&C bot agents, though Perl agents are still vastly more popular. The LMD project currently has classified 44 unique C&C bot agents comprising 286 agent scripts/binaries, 14 classes or 38 scripts of which are PHP based and 21 classes or 213 scripts of which are Perl based, 9 classes or 35 scripts/binaries being Other (c/ruby/java).

Currently there is an average of 6 bot networks being abuse reported per day, of those only about 2-3 per day ever receive any form of followup and/or shutdown of the host running the network. That is a rate of less than 50% on average, which is abysmal to say the least. When the threat management portal goes up in the coming weeks, these networks will find themselves at the top of the threat feed and planted squarely on the front page of the portal — we might not be able to shut them down but we sure can filter them off our networks.